1. Field of the Invention
The present invention relates generally to a mobile terminal that receives GPS (Global Positioning System) signals, and in particular, to a method of receiving GPS signals in a mobile terminal in a CDMA (Code Division Multiple Access) communication system.
2. Description of the Related Art
As mobile communication technology has evolved from second generation (2G) mobile communication systems to third generation (3G) mobile communication systems, a variety of contents have become available to users over a mobile communication network. For low-rate data transmission, the mobile communication network modulates data in QPSK (Quadrature Phase Shift Keying) and for high-rate data transmission, it modulates data in QAM (Quadrature Amplitude Modulation). This communication scheme is specified in the 1xEV-DO (Evolution-Data Only) and 1xEV-DV (Evolution-Data and Voice) standards. A terminal supporting the communication scheme has two reception paths to support diversity. Also, the use of GPS is becoming widespread to determine the locations of terminals.
FIGS. 1A and 1B are schematic block diagrams of a transmitter/receiver in a mobile terminal, for receiving GPS signals by a conventional method.
Referring to FIGS. 1A and 1B, a transmitter/receiver 100 in the conventional mobile terminal includes a sub reception path 130, a main reception path 150, and a transmission path 170. The main reception path 150 has a GPS reception path 151 and a CDMA reception path 155.
A switch 110 connected to an antenna decides whether to receive a GPS signal or a CDMA signal for a voice call in the mobile terminal. If the switch 110 selects the GPS signal, it switches data received through the antenna to a MODEM 190 through the GPS reception path 151. On the other hand, if the switch 110 selects the CDMA signal, it switches data received through the antenna to the MODEM 190 through the CDMA reception path 155. A duplexer 120 separates transmission and reception frequency bands of the mobile terminal.
The sub reception path 130 receives high-rate data and delivers it to the MODEM 190.
FIG. 1A schematically illustrates the above-described configuration and FIG. 1B is a more detailed block diagram of the transmitter/receiver 100 illustrated in FIG. 1A.
Referring to FIG. 1B, devices commonly used to receive a GPS signal or a CDMA signal, include a low pass filter provided in the main reception path 150. Therefore, it is impossible for the conventional mobile terminal to simultaneously receive the CDMA signal and the GPS signal via the main reception path 150. Traditionally, the main reception path 150 receives the CDMA signal or the GPS signal by time division. In this case, if the mobile terminal operates outdoors, it can capture a plurality of signals from GPS satellites for a time assigned for GPS signal reception due to its high received power. However, indoors the received power of the mobile terminal becomes weak, making it difficult to capture the GPS satellite signals without interrupting on-going CDMA signal reception, that is, without disconnecting a call. Especially, capturing GPS satellite signals concurrently with CDMA signal reception must be successfully completed in less than about 5 seconds, which imposes a great constraint on conventional mobile terminals.